If there is a long time interval (system delay time) from a time point (event detection time point) when a detector (sensor) provided on a road detects a situation (event) on the road to a time point (reception time point) when a receiver in a vehicle receives traffic guide information (detection data) based on the detection, there is the following problem: the received traffic guide information indicates old information (low reliable information). As a countermeasure against this problem, Patent Document 1 describes a device that acquires in advance an average value of the system delay time (average system delay time) in an information provision system, subtracts the average system delay time from the reception time point when the vehicle receives the traffic guide information, and thus estimates (calculates) the event detection time point. With the device, it is possible to remove, from the received traffic guide information, old information (low reliable information) detected at a time point (past time point) five minutes or more before the current time.
Patent Document 2 describes a vehicle-mounted device for identifying the same vehicle, by using travel information produced as a consequence of detecting an event by a detector (sensor) installed in a vehicle and information received by a communication terminal in this vehicle (travel information transmitted from another vehicle). In the vehicle-mounted device, the sensor, the communication terminal, a controller, the GPS (Global Positioning System) and a control ECU (Electronic Control Unit) for controlling an engine and a brake are connected with each other, through a bus of a CAN (Controller Area Network) which is an in-car network. Information indicating the result of the detection by the detector installed in the vehicle (own vehicle) is produced at intervals of 100 milliseconds. Information detected by the another vehicle is transmitted from a communication terminal (transmitter) in the another vehicle at intervals of several hundred milliseconds. If a time point indicated in time-point information added to the information received by the vehicle (own vehicle) is a time point (past time point) a threshold value or more before the current time, the received information is old information (low reliable information) and accordingly the information is removed.